Uncontrolled sweet clover cloaks Makoshika Park in gold

It’s big, showy, it smells good and if you’ve spent any time in Makoshika State Park this summer you’ve seen lots and lots of it covering the park’s grasslands from top to bottom.

Those extensive patches of golden flowers waving in the summer breeze are yellow sweet clover plants. And they don’t belong.

As ubiquitous as it is across Makoshika and much of the northern plains this summer, yellow sweet clover is not native to North America, but to Eurasia.

Sweet clover — there are yellow and white varieties — was introduced in the 1600s. It is not a true clover, but rather a legume, a member of the pea family.

As a forage crop, sweet clover gets eaten and its seeds spread by wildlife, which is almost assuredly how it ended up in Makoshika in the first place. One look across Makoshika’s prairie this summer provided a prime example of how quickly the plant can spread and how completely it can take over a grassland.

Given that it’s a non-native plant which spreads rapidly in large stands, you might think Montana State Parks would work to control its spread in Makoshika, but that’s not the case.

“It’s not a state noxious weed, so we don’t control it,” said Doug Habermann, Region 5 parks manager. “It’s not our policy to do it.”

In short, sweet clover, though non-native and despite its pervasive tendencies, is not considered an invasive plant in Montana.

“Historically, it was seeded a lot in the Great Plains, which is why we have it,” Mangold said. “A lot of people think of it as beneficial because it does provide forage and it’s a nitrogen fixer. In my experience, I don’t come across many people who rank it up there as a troublesome, invasive plant.”

That’s not to say, however, that sweet clover doesn’t have the potential to negatively impact native prairie.

“The potential detrimental effects would be it’s a large, robust plant, and it’s going to be using a lot of the water and nutrients to become that robust,” Mangold said. “So it could potentially be detrimental to other species.”

Minnesota, Missouri and Wisconsin are three states where sweet clover was historically planted as a cover crop which have now labeled it invasive.

Mangold said the fact sweet clover has been classified as invasive in other states shows attitudes towards non-native plants are constantly evolving.

“There are other species we can think of that we planted 40-50 years ago in an effort to improve rangeland that we no longer seed because we’ve seen they have invasive tendencies,” she said.

Mangold also said that in her time working with MSU Extension, she has never recommended planting sweet clover to a producer, adding that her “perception” is it’s not being planted by farmers “like it was 50 years ago,” which she thinks is a good thing.

Meanwhile, Makoshika is not the only public parkland in the area to be overrun with sweet clover this summer.

Theodore Roosevelt National Park Superintendent Valerie Naylor said the plant is widespread throughout the park, and has grown so high in the North Unit it’s causing problems for visitors by blocking out trail markers.

However, the National Park Service also does not try to control sweet clover in TRNP. Though the park service doesn’t like the plant’s presence, Naylor said it’s simply not worth the time and effort to try and control it.

If there is one silver lining to this summer’s infestation of area parkland by sweet clover, it’s this — the plant is a biennial, meaning the seeds only sprout and grow every two years.

“As a biennial, it probably won’t be like this next year,” Naylor said.